For treating patients with impaired kidney function, treatments by purifying blood by dialysis or filtration via semipermeable membrane have been provided conventionally. As for this apparatus, it is important to appropriately maintain the blood volume circulating in the patient body, to perform safe and effective blood purification. A rapid or excessive water removal will decrease excessively patient's blood circulating volume, and it may cause reduction of blood pressure, shock or the like. On the contrary, if the water removal is slow, it will take a long time for blood purification, and if sufficient water removal cannot be made, there is a fear that hypertension, heart failure or the like can occur.
Therefore, a hemodialysis apparatus performing water removal by monitoring patients blood condition have been developed. For example, in Japanese Laid-Open Patent Publication No. 6-83723, an estimating apparatus which estimates the body fluid condition with a Hematocrit meter, and a controlling apparatus which controls the blood pump or ultra pressure by the output of the estimating apparatus are described. Concerning this apparatus, it is convenient as the water removal is controlled directly according to the measured body fluid condition, but on the other hand, as the water removal is controlled directly by the measured value, in case the measuring means is not accurate or a trouble happens, it may cause a significant problem. Therefore, in such feed-forward control, generally, a separate line independent from the control line is disposed and a safety mechanism is loaded on the line. However, the apparatus becomes complicated when an independent line or safety mechanism is disposed and the operation becomes difficult. Furthermore, the cost of the apparatus will rise.
Therefore, a simple apparatus as described in Japanese Laid-Open Patent Application No. 9-149935 was also developed. In other words, while monitoring the patient's blood condition, an alarm is ringed depending to the condition, and the water removal pump is stopped. However, this apparatus only recognizes if the water removal control is performed under the same control condition at the time of the initiation of dialysis, by comparing with the blood concentration measured before the initiation of dialysis, and it is not possible to perform adequate water removal to each patent. Furthermore, if the water removal is not performed according to the condition, the operator has to adjust each time the water removal volume or substitutive fluid volume. Thus, even though it was safe, it was complicated and the human cost was high. Moreover, as for the apparatus, a means for measuring the blood condition is disposed on the line at the vein fluid side of the blood cycle, the blood condition after having passed the blood treatment machine (dialyzer) is measured, thus it may not reflect the patient's direct blood condition.
To provide a blood treatment apparatus which have solved the problems mentioned above, that is, to provide a convenient apparatus at a low cost by making a structure wherein each patient's blood condition is monitored, enabling to perform blood treatment adequate to each patient chronologically, by not imposing much burden to the operator during its use, and by making the construction of the blood treatment apparatus simple, the present inventors provided a blood treatment apparatus (Japanese Laid-Open Patent Application No. 11-22175), comprising a blood measuring means for measuring blood parameters; a working unit for performing blood treatment; and a controlling unit controlling the working unit to perform blood treatment under prescribed blood treatment condition, wherein the controlling unit indicates the change of the blood treatment to the working unit, by setting a blood indication region determined beforehand against the patient blood indication level obtained with the blood measuring means, according to the chronological transition of the blood indication level in the blood indication region. Furthermore, the present inventors have improved the blood treatment apparatus (Japanese Laid-Open Patent Application No. 11-22175), and proposed a blood treatment apparatus (Japanese Laid-Open Patent Application No. 2001-540), wherein by monitoring each patient's blood condition, the condition of hemodialysis adequate to each patient chronologically, especially the water removal speed can be easily changed and defined. Said blood treatment apparatus (Japanese Laid-Open Patent Application No. 2001-540) is a hemodialysis apparatus comprising at least: (A) a blood measuring means for measuring blood parameter, (B) a working unit for performing blood treatment; and (C) a controlling unit for controlling the working unit to perform blood treatment under prescribed blood treatment condition; wherein the hemodialysis apparatus has a mechanism for controlling the water removal speed, and the controlling unit (C) incorporates the blood indicating level obtained from the patients' samples by the blood measuring means (A), monitoring if it transits or not within the defined range defined beforehand of blood indication level (hereinafter also referred to as defined range of blood indication level), and when the blood indication level being the target to control deviates from the range defined beforehand, the water removal speed of the working unit (B) can be changed at a speed rate defined beforehand.
As for the hemodialysis apparatus mentioned above, it was possible to manage surely the blood indication level at each point during hemodialysis treatment, but because it was necessary to define the region of the target blood indication level at each point, the operation was complicated. Furthermore, as the defined blood indication level was designated as a range, as long as a blood indication level exists within the defined range (even it is at the absolute edge of the range), the control mechanism of the hemodialysis apparatus would not work. Therefore, in case the blood indication level actually measured is slightly missing the point from the target, there was a fear that the control would be delayed.